Free Idea #2 High Altitude Rocket Launch

Concept idea i was just thinking about for a new style rocket. Modern rockets are heavy. They require at least one set of thrusters and a ton of fuel just to get high enough in the atmosphere to launch a secondary set of thrusters to push outer earth orbit. Space X estimates 200,000 to 300,000 dollars on fuel for the falcon 9

My idea is to build a platform with multiple high altitude balloons. The edge of this platform will be equipped with multiple engines. These engine engage when the high altitude balloons reach maximum altitude. At this point the rocket platform launches, Forcing the payload higher into the atmosphere. The payload is attached to a slingshot like device in the center of the platform. As the platform rushes higher into space either resistance or reverse thrusting engine causes tension on the slingshot. Before the platform reaches its maximum altitude the resistance/reverse thrusting payload is released and slingshots into orbit. This idea is still rough and i do have a few more ideas on optimizing. like hollow point of the platform working like a rail gun. as the payload moves through the platform it bursts like a coil gun or electromagnet. Ill update soon. Thanks for looking